This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined at the end of the specification but prior to the claims.
There is a 3GPP Release 12 feature “Further enhancement to LTE TDD for DL-UL Interference Management and Traffic Adaptation (TDD_eIMTA)”. The goal of eIMTA WI is to enable more flexible TDD UL-DL reconfiguration for traffic adaptation in, e.g., small cells. The starting point following the Rel-12 assumptions is that the eNodeB (e.g., for the small cell) may vary the UL-DL configuration relatively often (for those UEs configured to flexible UL/DL mode) compared to the existing situation where the UL-DL configuration is in practice very stationary.
In this disclosure, focus is placed on PUCCH resource allocation, e.g., for TDD eIMTA. It has been decided to arrange HARQ/scheduling timing for eIMTA according to a so-called reference configuration principle, where different but existing TDD configurations define HARQ/scheduling timing for uplink and downlink. The related decisions after 3GPP RAN1#75 meeting (11-15, Nov. 2013) are summarized below:                For a UE configured with TDD eIMTA, uplink scheduling timing and HARQ timing follow UL-DL configuration signaled in SIB-1;        DL HARQ reference configuration can choose from Rel-8 TDD UL-DL configurations {2, 4, 5};        A subframe configured as DL subframe or DwPTS of special subframe in SIB-1 (in case of PCell) and RadioResourceConfigCommonSCell IE (in case of SCell) should not be used for uplink transmission.        Under any valid UL and DL HARQ reference configurations, the UE should not expect any subframe configured as UL subframe or special subframe in DL HARQ reference configuration is dynamically used as DL subframe.        
These decisions may lead to problems with conflicts for HARQ information, as described in more detail below.